Diesel engines are increasingly being used in automobiles, trucks and heavy equipment because they are more rugged and efficient than their gasoline counterparts and have longer life expectancies. The diesel engine does, however, experience some problems which are not encountered in gasoline powered engines. One of these problems is the difficulty of starting a diesel engine in cold weather.
In a diesel engine, combustion takes place when air, compressed in the engine cylinders, reaches the ignition temperature of the diesel fuel. In warm weather, the intake air can easily reach the fuel ignition temperature when it is compressed. However, when a cold engine is started, some of the heat generated by the compression of the air in the cylinders is dissipated to the engine parts and this heat-sinking effect may result in the air not reaching the ignition temperature upon compression. Thus, at colder temperatures, especially below freezing, the heat produced by compression may not be able to overcome the heat-sinking effects of the cold engine. Indeed, it can be quite difficult, even impossible, to start a diesel engine in very cold weather conditions.
Many techniques for alleviating engine cold start problems have been proposed and developed. Essentially, in order to counter the heat-sinking effects of the cold engine parts, the engine must be supplied with additional heat from one source or another. Current engine cold start aids make use of three different sources of thermal energy. There are some preheater systems which convert electrical energy from the engine battery or an external outlet into thermal energy. Some known systems employ small fuel burners which draw fuel from the main tank in order to provide heat. Some preheaters produce heat by other forms of chemical burning. In all of these prior systems, the thermal energy produced is used to heat oil in the engine crankcase and/or engine intake air to assist the starting of the engine. However, they all have certain drawbacks which militate against their being considered the ultimate solution to the cold start problem.
The systems which derive their heat from a battery tend to drain the battery, which itself does not operate efficiently in cold weather. Also, in many cases, an external electrical source is not available. Those systems which produce heat by fuel or the burning of other chemicals can present a hazard when operating for long periods in a confined space because they generate poisonous or noxious fumes.